Apparatus for the epitaxial growth of semiconducting material by liquid phase epitaxy from at least two source solutions

ABSTRACT

An apparatus is disclosed for the epitaxial growth of semiconducting material by liquid phase epitaxy from at least two source solutions. A reaction chamber is designed of separable parts and can be suitably opened. Included within the reaction chamber are substrate wafers and the source solutions. The reaction chamber can be established within a furnace having temperature control means. It is capable of rotation about its axis which is a hollow tube. There are provided within the reaction chamber separating walls and baffles which form channels such that the substrate wafers are brought into contact by gravity with one of the source solutions at a time or are removed therefrom dependent on the rotation angle and on the number of completed revolutions of the reaction chamber.

United States Patent 1191 Scheel 1451 Jan. 7, 1975 1 APPARATUS FOR THE EPITAXIAL GROWTH OF SEMICONDUCTING MATERIAL BY LIQUID PHASE EPITAXY FROM AT LEAST TWO SOURCE SOLUTIONS [75] Inventor: Hans-Jiirg Scheel, Kilchberg,

Switzerland [73] Assignee: International Business Machines Corporation, Armonk, NY.

22 Filed: Nov. 12,1973

21 Appl. No.: 415,272

[30] Foreign Application Priority Data [56] References Cited UNITED STATES PATENTS 553,547 l/l896 Tyler, Jr 118/425 UX 2,042,559 6/1936 Stelkens 118/421 X Bergh 118/421 Primary Examiner-Morris Kaplan Attorney, Agent, or Firm-Bernard N. Wiener [57] ABSTRACT An apparatus is disclosed for the epitaxial growth of semiconducting material by liquid phase epitaxy from at least two source solutions. A reaction chamber is designed of separable parts and can be suitably opened. Included within the reaction chamber are substrate wafers and the source solutions. The reaction chamber can be established within a furnace having temperature control means. It is capable of rotation aboutits axis which is a hollow tube. There are provided within the reaction chamber separating walls and baffles which form channels such that the substrate wafers are brought into contact by gravity with one of the source solutions at a time or are removed therefrom dependent on the rotation angle and on the number of completed revolutions of the reaction chamber.

14 Claims, 10 Drawing Figures 2 Sheets-Sheet 1 Patented Jan. 7, 1975 3,858,553

2 Sheets-Sheet 2 GAS SOURCE OUT F l G; 1 A 2-4 2-8 DR'VER R.F. POWER APPARATUS FOR THE EPITAXIAL GROWTH OF SEMICONDUCTING MATERIAL BY LIQUID PHASE EPITAXY FROM AT LEAST TWO SOURCE SOLUTIONS BACKGROUND OF THE INVENTION At least two source solutions are useful for producing certain semiconductor structures, e.g., graded structures, by liquid phase epitaxy. When fabricating semiconductor elements with a PN-junction, it is advantageous to have at least two suitably doped source solutions available in the growth apparatus to facilitate solution exchange. It is desirable to have a controllable solution exchange, especially in the fabrication of superlattice structures which may be structures of thin layers of semiconductors with alternating types of conductivity. In this kind of structure there exists a pcriodically changing potential across the device which provides specific operational quantum effects. Reference is made to the background paper by L. Esaki et al. Superlattice and Negative Differential Conductivityv in Semiconductors which appeared in the IBM Journal of Research and Development, Vol. 14, Issue 1 (Jan. 1970, pp. 61 through 65). Further, there may be fabricated graded structures with a doping profile varying normal to the plane of layers.

In the prior art, us. Pat. No. 3,551,219 describes an apparatus for'liquid phase epitaxy with the substrate on which growth is to occur attached to the lower side of a slide. The substrate can be brought into contact with either of two solutions. Another prior art apparatus is described in US. Pat. No. 3,565,702 in which the substrate is established in a slide which can be moved below containers with the different source solutions. These prior art types of apparatus are usually suitable only for a fabrication technique in which a single substrate wafer can be used at a time.

Further, a rotary reactor for liquid phase epitaxy from only one source solution is described by the paper by J. Vilms et al. The Growth and Properties of LPE GaAs which appeared in Solid State Electronics on pages 443 through 455 of Vol. 15, 1972. This reactor can be established in a temperature-controlled oven, and its hollow axis is designed as inlet and outlet of gaseous substances. Depending on the cylindrical reactor size, several substrate wafers may be grown upon at a time within this apparatus. However, it is not possible to exchange several source solutions in this latter apparatus.

Copending U.S. Pat. application Ser. No. 64,523 tiled Aug. 5, 1970 by J. Grandia et al., assigned to the same assignee and now abandoned and refiled as copending continuation in part application Ser. No. 360,518 on May 15, 1973, describes an apparatus for isothermal solution mixing growth of solids in which portions of several source solutions are transported for growth purposes.

SUMMARY OF THE INVENTION It is an object of the invention to provide an apparatus for the epitaxial growth of semiconducting material by liquid phase epitaxy from at least two source solutions which can be exchanged in the apparatus.

The invention relates to an apparatus for the epitaxial growth of semiconducting material by liquid phase epitaxy from at least two source solutions comprising a reaction chamber which is designed of separable parts and can be suitably opened. Included in the reaction chamber are substrate wafers and source solutions. The chamber can be established within a furnace having temperature control means. It is capable of rotation about its axis which is designed as inlet or outlet of a gaseous substance which may be a protective gas or a reactant.

The apparatus of this invention is characterized by walls and baffles which define separate sections in the reaction chamber and form channels within the reaction chamber in such a way that the source solutions are brought one at a time into contact with the appropriate substrate wafers or the solution is removed from the respective substrate wafers dependent on the rotation angle and on the number of completed revolutions of the reaction chamber.

. In one embodiment of the invention, the substrates are in contact with one of the source solutions within the reaction chamber in a certain range of rotation angle of the reaction chamber, while the other source solution is in an open or closed channel at the same time. In another embodiment, some of the substrates are within one of the source solutions and others are within the other source solution. Cyclically, after completion of a revolution of the reaction chamber, both solutions are exchanged.

The foregoing and other objects, features and advantages of the invention-will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings.

DRAWINGS FOR THE INVENTION FIG. 1 illustrates schematically a perspective view of the exterior of the cylindrical reaction chamber.

FIG. 1A is a schematic perspective view illustrating the reaction chamber of FIG. 1 in an operable condition for liquid phase epitaxy.

FIG. 2 illustrates the separable part of the reaction chamber including several substrates on which layers are to be grown.

FIG. 3 is a cross-sectional view of the reaction chamber of FIG. 1 taken normal to its axis.

FIG. 4 illustrates schematically a development view of the cylindrical reaction chamber showing the arrangement of the separation walls and baffles of a first embodiment of the invention in which one of the source solutions is in an open middle channel while the other source solution wets the substrates in two outer channels.

FIG. 4A illustrates a perspective view of the interior of the first embodiment of the invention as illustrated in FIG. 4.

FIG. 5 illustrates schematically a development view of the cylindrical reaction chamber showing the arrangement of the separation walls and baffles of a second embodiment of the invention in which one of the source solutions is in a closed channel while the other source solution wets the substrates.

FIG. 5A illustrates a perspective view of the interior of the second embodiment of the invention as illustrated in FIG. 5.

FIG. 6 illustrates schematically a development view of the cylindrical reaction chamber showing the arrangement of the separation walls and baffles of a third embodiment of the invention in which one of the source solutions wets a first group of substrates in the left section while simultaneously the other source solution wets a second group of substrates in the right section. a

FIG. 7 illustrates a perspective view of the interior of the third embodiment of the invention as illustrated in FIG. 6.

EMBODIMENTS OF THE INVENTION As shown in the perspective view of FIG. 1, the cylindrical reaction chamber consists of two parts, illustratively, a larger part 1 connected to an axial tube 2 and a detachable smaller part 3. Illustratively, the separable parts could also be provided normal to the axis, e.g., the front face 7 may be detachable. It is only essential that it is possible to open or to separate the reaction chamber in order to have access to its interior, and that the axial tube 2 communicate with the interior of the reaction chamber to facilitate gas exchange therein. Gas is introduced via tube 2 at inlet 2-1 from gas source 2-2 and removed via outlet 2-3. Further, as shown in FIG. 1A, driver 24 causes the chamber to rotate counterclockwise as shown by arrow 2-5. The reaction chamber is established in furnace 2-6 having windings 2-7 which are energized by controllable radiofrequency power source 2-8.

FIG. 2 illustrates the smaller part 3 from the interior of the reaction chamber, including a row of substrates 4 fastened with clamps 4-1. In this arrangement, another batch of substrates on which layers are to be grown can be exchanged easily while the source solutions remain undisturbed in the lower part 1. FIG. 3 shows a cross-sectional view of FIG. 1. Solution 5 is not disturbed by loading or unloading of substrates 4. Rim 6, which extends along a surface line, facilitates wetting of the substrates 4 when the reaction chamber is rotated.

The reaction chamber is formed of a material which is chemically neutral and which withstands the high temperature of the liquid phase epitaxy, e.g., graphite or vitreous carbon. However, if the semiconducting material contains oxides, a suitable material, e.g., noble metal, must be chosen as the material of the reaction chamber. Axial tube 2 is hollow and communicates with the interior of the reaction chamber to allow passing of gaseous substrates which are protective gases, reactants or carriers of dopants. It is advantageous to keep the reaction chamber within an envelope, e.g., to seal the reaction chamber from the environment. In this circumstance, the furnace 2-6 comprises a quartz tube with a protective gas therein via an inlet not shown. Such protective gas can also be introduced within the furnace 2-6 via tube 2.

During epitaxial growth the rotatable reaction chamber is arranged within a temperature-controlled heating means. This maybe, for example, a horizontal split tube furnace having axially extending heating elements so that the furnace can be opened and loaded easily. If the furnace is provided with angular heating elements, e.g., radiofrequency heating coils, the apparatus must be built so that it is movable axially to be transferred into the heating means or removed therefrom. The heat supply should be controlled to keep the temperature within an error of less than 0.lC of the desired value.

The heating means and the driver means are operated cooperatively to meet the requirements for the exemplary liquid phase epitaxial growth procedures described later herein.

FIGS. 4, 5, and 6 are related to the perspective views of FIGS. 4A, 5A and 7 which illustrate the interiors of the respective reaction chambers. These figures are useful for explaining several design principles on which the mechanical fluid separation system of the invention is based. Each of'FIGS. 4, 5 and 6 is a development of the related cylindrical reaction chamber rolled into the drawing plane. The circumferences of front face 7 and end face 8 of the cylindrical reaction chamber appear in FIGS. 4, 5 and 6 as vertical straight lines on the left side and on the right side, respectively. The pattern is repeated after a complete circumference of the respective cylindrical reaction chamber is developed. For clarity of illustration, there is developed more than one complete revolution of the respective reaction chamber. A scale entry of angle 360 is shown for a complete revolution which identifies the areas of the developedfigures which are repeated.

FIGS. 4 and 4A illustrate an embodiment of the apparatus according to the invention. There are two operating melts or solutions A and B. Illustratively, solution A can wet substrates in the reaction region 9, while at the same time solution B is separated from solution A in open channel 10. After completion of one revolution of the cylindrical reaction chamber, both solutions are exchanged such that solution B is in contact with the substrates and solution A is in open channel 10. Separation walls or baffles 12 and 13 extend in radial direction to a height of about a third of the diameter of the cylinder 1 and they confine reaction region 9. At a location, e.g., in the middle, separation walls or baffles 12 and 13 change to channelwalls or baffles 14 and 15, respectively. Channel 10 penetrates separation wall 13 with orifice 11. The orifice of the channel 10 entering the reaction region is arranged above a transverse rim 6 to ensure that all of the substrates 4 are wetted in one action during rotation of the reaction chamber. Channel 10 built in this manner does lead through reaction region 9 in the middle, but it may alsolead to a side. Channel 10 extends to the cylinder surface. It may also lead through the reaction region like a trough-shaped bridge. The profile of channel 10 need only be chosen so it can absorb a suitable amount of an operating fluid at a time.

FIGS. 5 and 5A illustrate an embodiment of the invention comprising a closed channel 10 which may have the shape of a pipe or tube leading through the reaction region. Parts of FIGS. 5 and 5A which are comparable to those in FIGS. 4 and 4A bear similar numbers. A transverse separation wall 16 confines the reaction region 9 including substrates 4 and solution A. At this time solution B is within the closed channel 10 extending between the orifices l7 and 18 which penetrate separation wall 16. In this embodiment, both solutions A and B exchange places after each completed revolution of the reaction chamber.

The development view of FIG. 6 and the perspective drawing of .FIG. 7 illustrate an embodiment of the apparatus according to the invention comprising an intermediate separation wall 19 separating two reaction regions 20 and 21 from each other, each of which contains some of substrates 4 on which there is to be growth by liquid phase epitaxy. Intermediate separation wall 19 extends parallel to the end faces 7 and 8 of the cylindrical reaction chamber, and is penetrated by the tube 2. Separation wall 22 between front face 7 and intermediate separation wall 19 confines reaction region 20. Separation wall 23 between the intermediate separation wall 19 and the end face 8 confines the reaction region 21. The short channels 24 and 25 are staggered with respect to the circumference of the cylinder to ensure that reaction region 21 is first emptied of the fluid present therein through orifice 24 just before the other fluid flows in through orifice 25. In this embodiment, there is always one of the source solutions within one reaction region when the other of the source solutions is in the other reaction region. The solutions A and B are exchanged after each complete revolution of the cylindrical reaction chamber. Both reaction regions may also be loaded with different gases if orifices 24 and 25 are provided with flap valves, not shown, or other suitable means.

PRACTICE OF THE INVENTION After first loading the reaction chamber with the source materials and with the substrates, the chamber is rotated into a position within the furnace such that the substrates are out of contact with the source materials to be melted. Gas flow, e.g., hydrogen, through the sealed reaction chamber is adjusted, and the closed furnace is brought to a temperature higher than the actual liquid phase epitaxial growth temperature. Several preliminary revolutions are desirably undertaken with the reactor containing the heated source solutions in order to etch the growth surface of the substrate. The furnace is then adjusted to the lower growth temperature. During the cooling program of the liquid phase epitaxy, the reaction chamber is rotated so that epitaxial growth of the desired layer takes place from the liquid phase. The growth can be influenced by altering the speed of rota tion. The thickness of the undisturbed boundary layer on the substrate can be diminished by relative motion between solution and substrate, and the crystal growth is favorably enhanced. Further, the thickness of the growing layer can be controlled by proper choice of speed of rotation of the reaction chamber. This is especially important for the fabrication of alternating very thin layers with different properties. After having reached the desired layer thickness or structure, slow cooling down to room temperature takes place by establishing an angular position of the reaction chamber where the substrates are out of contact with the source solution.

The apparatus of this invention is useful for the fabrication of semiconductor devices, e.g., layered and graded structures, using Ill-V compounds such as GaAs or lnP. In the melted state the source solutions exhibit a high surface tension such that the reaction chamber, e.g., of graphite, is not wetted. Therefore, the apparatus according to the invention is suitable for growing alternately different layers. By controlled rotation, e.g., continuous rotation, the substrates for growth by liquid phase epitaxy are brought into contact with the source solutions which are supersaturated by the controlled cooling. The periodicity of the structure being fabricated is controlled by the number of completed revolutions of the cylindrical reaction chamber. The thickness of a single layer depends on the amount of supersaturation of the source solution as well as on the ratio of substrate surface area to the volume of the solution and further on the wetting time which is controlled by the speed or velocity of rotation.

The relative supersaturation of a source solution in the boundary layer near the growing crystal is related concentration is the concentration where solid solute and solution are in equilibrium. lllustratively, depending on such parameters as the relative supersaturation, the temperature and the solution flow-rate relative to the substrate, the linear growth rate normal to the substrate plane can be adjusted to be between 10 Angstroms per second and 1,000 Angstroms per second. Low growth rates and low temperatures are used for preparation of very thin layers of especial quality. These layers exhibit low dislocation density. High growth rates and relatively high temperatures are used for preparation of thick layers and for high production rates. High solution flow-rates are favorable for obtaining smooth flat layers. The obtainable intensity of relative supersaturationis determined by several factors, each of which can itself be influenced. The cooling rate is chosen with respect to the liquidus temperature of the corresponding phase diagram. The ratio of total substrate surface areas to volume of the solution also influences the liquid phase epitaxial growth. Further, the material transport rate can be influenced by proper choice of temperature gradient. Further, the flow-rate of any gaseous supply has to be considered for influence on the liquid phase epitaxial growth if these gases contain reactants or dopants.

The effective solution flow-rate can also be increased at low rotation rates of the reaction chamber if that chamber is not rotated continuously but is rotated backward and forward in an angular range of about plus or minus 20", with the substrates remaining in the respective source solution. When the layer has grown to the desired thickness, the reaction chamber is rotated in such'a way that the substrates either are out of contact with one source solution or are wet by another source solution. The growth temperature normally lies between about 300C and 1,200C. For a particular embodiment, the maximum practicable container rotation rate will be approximately 20 revolutions per minute. The stirring effect caused by the rotation of the cylindrical reaction chamber diminishes the thickness of the diffusion boundary layer near the growing crystal interface so that the growth rate becomes very sensitive to changes in supersaturation. Therefore, it is important to control the temperature within a maximum error value of less than 01C. The obtainable layer thickness can be adjusted between about Angstroms and several microns within narrow tolerances.

Semiconductor structures which in the literature are termed superlattice structures exhibit a periodicity which is less than the mean free path of electrons, e.g., about 100 Angstroms. lllustratively, there'will now be described a procedure for the preparation of Ga, Al As superlattice structures. First, the source solutions A and B are prepared. Solution A contains 50 gms of Ga, 0.05 gms of Al, 0.01 gms of Te. These source materials are mixed with an appropriate amount of pure GaAs such that the solution is saturated at 825C. Solution B contains 50 gms of Ga, 0.10 gms of Al and 0.0l gms of Te, and is also saturated with pure GaAs at 825C. The reaction chamber is loaded with the substrates. e.g., single crystalline wafers of GaAs, for liquidphase epitaxy and with both solutions A and B. After flushing the reaction chamber with protective gas and after etching the substrate surfaces when desired as described hereinbefore, the starting temperature of 825C is established. To achieve the necessary relative supersaturation, the liquid phase epitaxy requires a cooling rate of approximately O.lC per minute. With the aid of a conventional electronic control device, the. power to the electric furnace is controlled according to the desired cooling program. The precision of temperature control should be approximately 0.0lC. The apparatus is rotated at l revolution per minute. After 100 minutes the end temperature of 815C is reached. In this way, 50 layers are grown of about 600 Angstroms thickness which correspond to the composition of solution A, alternating with SO layers which correspond to the composition of solution B of approximately the same thickness. If it is desired to grow thinner layers,

the apparatus is rotated faster. In this case, it is possible to operate with lower temperatures.

Graded structures of GaP can also be produced in a similar manner. For preparing layers of N-conductivity, source solution A contains Ca? in Ga and is doped with sulphur. For preparing layers of P-conductivity, source solution B contains GaP in Ga and is doped with zinc. A suitable substrate is a Ga? (1 11) substrate, for which a desirable temperature range is between l,lC and 1,050C.

CONSIDERATIONS FOR THE INVENTION If during growth of the layers the composition of a solution changes too much due to depletion, the heating and cooling must be changed accordingly. However, a given temperature program can be maintained if the material consumed is replenished in the apparatus in a suitable manner, e.g., through the vapor phase or by adding solid substance.

A gradual change of layer composition can also be accomplished to provide graded structures. These are semiconductor structures whose composition or conductivity characteristic changes successively transverse to the plane of the sandwiched layers. Semiconductor structures fabricated in this way can be used, e.g., for light emitting diodes and turnable semiconductor lasers.

According to the principle of the invention, the apparatus can also be built in such a way that more than two source solutions can be used to produce more complicated sandwiched structures of semiconductors, insulators or metals.

There have been described and illustrated several embodiments of this invention utilizing a container for treating a workpiece fixed in the container with at least two different liquids intermittently and alternately. The liquids are held temporarily in separable compartments or receptacles during rotation of the container about a given axis. Due to the rotation of the container, the liquids are exchanged between the compartments by mass movement via at least one channel interconnecting the compartments of the container.

In particular, the apparatus of this invention includes a cylindrical reaction chamber or container wherein a semiconducting layered structure is grown on a substrate by liquid phase epitaxy from at least two different solutions. The solutions are exchanged between the separable compartments where they are temporarily located. When the cylinder is rotated about its axis of revolution, the solutions are exchanged via a channel arrangement so that a given substrate fixed in said container in one of the compartments is contacted by the different solutions alternately. If the container is rotated continuously, the alternate layers of the semiconductor structure are grown periodically and each layer will be of approximately the same thickness.

What is claimed is:

1. Apparatus for treating a workpiece comprising a closed rotatable chamber which is adapted to include at least one said workpiece fixed relative to said chamber and to include at least two different source liquids contained in and movable in said chamber during rotation of said chamber about an axis, said chamber havmg:

a plurality of channels formed by a plurality of walls to hold temporarily each said source liquid away from said workpiece and to distribute successively said source liquids onto said workpiece during said rotation about said axis.

2. Apparatus according to claim 1 wherein said chamber is cylindrical,

a treating region of said chamber formed by said walls contains said workpiece, and

a channel formed by said walls holds one of said liquids while the other said liquids is in contact with said workpiece.

3. Apparatus according to claim 2 wherein the said chamber wall at said treating region is configured to define a ridge extending into said chamber to enhance wetting of said workpiece during said rotation of said chamber.

'4. Apparatus according to claim 2 wherein an open channel formed by said walls passes through said treating region and distributes each said liquid to said reaction region after one complete revolution of said chamber.

5. Apparatus according to claim 4 wherein said open channel is formed in a funnel shape by two walls, which shape distributes said liquids via an orifice thereof.

6. Apparatus according to claim 2 wherein a closed channel extends between a first orifice in a wall of said treating region and a second orifice in said wall, said closed channel holding one said liquid during the time the other said solution is in said treating region.

7. Apparatus according to claim 2 wherein said walls form two treating regions containing at least one workpiece each, and

said walls form a region for holding one said liquid while the other said solution is partially present in each of said two treating regions.

8. Apparatus for the growth of semiconducting material by liquid phase epitaxy having a closed reaction chamber which is adapted to include at least one substrate fixed relative to said chamber on which said semiconducting material is to be grown from at least two different source solutions contained in and movable in said chamber during rotation of said chamber about an axis and which isadapted to be established in a furnace with temperature control means, said reaction chamber comprising:

a plurality of channels formed by a plurality of walls to hold periodically each said source solution away from said substrates and to distribute said source solutions successively onto said substrates according to the angle of rotation and number of completed revolutions of said reaction chamber about said axis.

9. Apparatus as set forth in claim 1 wherein:

said workpiece is a substrate,

said chamber is a rotatable reaction chamber for use in growth of a layered structure on said substrate by liquid phase epitaxy,

said channels comprise a plurality of interconnecting channels disposed to contain said plurality of different liquids, and

said axisis an axis of rotation of said chamber such that when said chamber is rotated said different liquids are distributed successively into one said channel separately and temporarily related to the angular rotation of said chamber about said axis.

10. Apparatus as set forth in claim 1 wherein:

said chamber is for use in growth of a layered structure by liquid phase epitaxy, and

said channels comprise a plurality of interconnecting channels adapted to hold respectively a plurality of volumes of said different liquids which through movement of said chamber are distributed successively and separately into and out of a given channel of said plurality of interconnecting channels.

11. Apparatus as set forth in claim 1 for exchanging the volumes of said two different liquids between two respective locations for treating at least one said workpiece in one of said locations intermittently and alternately with said different liquids, wherein:

said chamber is a container having at least two compartments adapted to hold separately said liquids,

said plurality of walls in said container form said compartments for holding said liquids intermittently, and

a plurality of baffles in said container are connected to said plurality of walls to form at least two said channels interconnecting said compartments so that during rotation of said container about said axis mass movement of said liquids via said channels effects exchange thereof between said compartments alternately in relationship to the angular rotation of said container.

12. Apparatus as set forth in claim 11 wherein said container is a cylinder and said rotation axis is the axis of revolution of said cylinder.

13. Apparatus as set forth in claim 1 for treating said workpiece with a plurality of said different liquids intermittently and alternately wherein:

said chamber is a container for said liquids,

two of said channels comprise at least two compartments in said container capable of holding separately said liquids, and

there is at least one said channel interconnecting said compartments for exchanging said liquids between said compartments by mass movement due to rotation of said container about said axis.

14. Apparatus as set forth in claim 12 wherein said container is a cylinder and said axis is the axis of revolution of said cylinder. 

1. Apparatus for treating a workpiece comprising a closed rotatable chamber which is adapted to include at least one said workpiece fixed relative to said chamber and to include at least two different source liquids contained in and movable in said chamber during rotation of said chamber about an axis, said chamber having: a plurality of channels formed by a plurality of walls to hold temporarily each said source liquid away from said workpiece and to distribute successively said source liquids onto said workpiece during said rotation about said axis.
 2. Apparatus according to claim 1 wherein said chamber is cylindrical, a treating region of said chamber formed by said walls contains said workpiece, and a channel formed by said walls holds one of said liquids while the other said liquids is in contact with said workpiece.
 3. Apparatus according to claim 2 wherein the said chamber wall at said treating region is configured to define a ridge extending into said chamber to enhance wetting of said workpiece during said rotation of said chamber.
 4. Apparatus according to claim 2 wherein an open channel formed by said walls passes through said treating region and distributes each said liquid to said reaction region after one complete revolution of said chamber.
 5. Apparatus according to claim 4 wherein said open channel is formed in a funnel shape by two walls, which shape distributes said liquids via an orifice thereof.
 6. Apparatus according to claim 2 wherein a closed channel extends between a first orifice in a wall of said treating region and a second orifice in said wall, said closed channel holding one said liquid during the time thE other said solution is in said treating region.
 7. Apparatus according to claim 2 wherein said walls form two treating regions containing at least one workpiece each, and said walls form a region for holding one said liquid while the other said solution is partially present in each of said two treating regions.
 8. Apparatus for the growth of semiconducting material by liquid phase epitaxy having a closed reaction chamber which is adapted to include at least one substrate fixed relative to said chamber on which said semiconducting material is to be grown from at least two different source solutions contained in and movable in said chamber during rotation of said chamber about an axis and which is adapted to be established in a furnace with temperature control means, said reaction chamber comprising: a plurality of channels formed by a plurality of walls to hold periodically each said source solution away from said substrates and to distribute said source solutions successively onto said substrates according to the angle of rotation and number of completed revolutions of said reaction chamber about said axis.
 9. Apparatus as set forth in claim 1 wherein: said workpiece is a substrate, said chamber is a rotatable reaction chamber for use in growth of a layered structure on said substrate by liquid phase epitaxy, said channels comprise a plurality of interconnecting channels disposed to contain said plurality of different liquids, and said axis is an axis of rotation of said chamber such that when said chamber is rotated said different liquids are distributed successively into one said channel separately and temporarily related to the angular rotation of said chamber about said axis.
 10. Apparatus as set forth in claim 1 wherein: said chamber is for use in growth of a layered structure by liquid phase epitaxy, and said channels comprise a plurality of interconnecting channels adapted to hold respectively a plurality of volumes of said different liquids which through movement of said chamber are distributed successively and separately into and out of a given channel of said plurality of interconnecting channels.
 11. Apparatus as set forth in claim 1 for exchanging the volumes of said two different liquids between two respective locations for treating at least one said workpiece in one of said locations intermittently and alternately with said different liquids, wherein: said chamber is a container having at least two compartments adapted to hold separately said liquids, said plurality of walls in said container form said compartments for holding said liquids intermittently, and a plurality of baffles in said container are connected to said plurality of walls to form at least two said channels interconnecting said compartments so that during rotation of said container about said axis mass movement of said liquids via said channels effects exchange thereof between said compartments alternately in relationship to the angular rotation of said container.
 12. Apparatus as set forth in claim 11 wherein said container is a cylinder and said rotation axis is the axis of revolution of said cylinder.
 13. Apparatus as set forth in claim 1 for treating said workpiece with a plurality of said different liquids intermittently and alternately wherein: said chamber is a container for said liquids, two of said channels comprise at least two compartments in said container capable of holding separately said liquids, and there is at least one said channel interconnecting said compartments for exchanging said liquids between said compartments by mass movement due to rotation of said container about said axis.
 14. Apparatus as set forth in claim 12 wherein said container is a cylinder and said axis is the axis of revolution of said cylinder. 